Electrochemical cells comprise a cathode, an anode and an electrolyte interposed therebetween. The electrochemical cells are often defined as liquid or solid cells and this refers merely to whether the electrolyte interposed between the anode and the cathode is a liquid or a solid. Solid electrochemical cells are well known in the art and present many advantages over conventional liquid batteries such as improved safety features, lighter weight, etc. Non-aqueous lithium electrochemical cells are discussed in U.S. Pat. Nos. 4,472,487, 4,668,595, 5,028,500, 5,441,830, 5,460,904, and 5,540,741.
The anode comprises a compatible anodic material which is any material which functions as an anode in an electrochemical cell. Such compatible anodic materials are well known in the art and include, by way of example, lithium, lithium alloys, such as alloys of lithium with aluminum, mercury, nickel, zinc, and the like, and intercalation based anodes such as carbon, WO.sub.3, and the like.
The cathode comprises a compatible cathodic material which refers to any material which functions as a positive pole (cathode) in an electrochemical cell. Such compatible cathodic materials are well known in the art and include, by way of example, manganese dioxide, molybdenum trioxide, sulfides of titanium and niobium, chromium oxide, copper oxide, vanadium oxides such as V.sub.2 O.sub.5, V.sub.6 O.sub.13, LiV.sub.3 O.sub.8 and the like. The particular compatible cathodic material employed is not critical. When the electrochemical cell is a secondary cell, then the compatible cathodic material employed is one which is capable of being recharged (e.g., LiV.sub.3 O.sub.8, V.sub.6 O.sub.13, MoO.sub.3, and the like).
Composite electrode refers to cathodes and anodes wherein the cathode is comprised of materials other than compatible cathodic materials and the anode is comprised of materials other than compatible anodic materials. Typically, the composite electrode contains a polymer which acts to bind the composite materials together and an electrolytic solvent. Composite electrodes are well known in the art. For example, a composite cathode can comprise a compatible cathodic material, a conductive material, an electrolytic solvent, an alkali salt, and a solid matrix forming polymer. Similarly, for example, a composite anode can comprise a compatible intercalation anodic material, an electrolytic solvent and a solid matrix forming polymer.
When fabricating electrochemical cells comprising composite electrodes, the anode is typically prepared by applying an anode mixture comprising a polymer, an anodic material and a carrier solvent to a substrate and then allowing the carrier solvent to evaporate or "air dry" to form an anode film. The anode film is then laminated onto a current collector to form the anode. Alternatively, the anode mixture can be applied directly to a current collector and the carrier solvent allowed to evaporate to form the anode. The cathode is typically prepared in a similar manner from a cathode mixture comprising a polymer, a cathode active material and a carrier solvent. Similarly, the separator is typically prepared by applying a layer of polymer mixture onto a substrate and allowing the solvent to evaporate. After cutting these components to the appropriate sizes and separating the substrates therefrom, the anode, separator, and cathode are laminated together.
Although this method of preparing electrochemical cells has been satisfactory, this technique tends to be expensive and time consuming. Accordingly, the art is in search of improved techniques of fabricating electrochemical cells that are cost effective and particularly suited for mass production.